Fluid pressure supply system



Jan. 14, 1969 v w, HEYER ET AL 3,421,795

FLUID PRESSURE SUPPLY SYSTEM Filed May 31, 1967 Sheet of 5 r f f? i. O N

l r E 5 9 INVENTOR WlLLI HEYER FRIEDRICH BRINKMANN Jan. 14, 1969 HEYER ET AL 3,421,795

FLUID PRESSURE SUPPLY SYSTEM Filed May 31, 19 7 Sheet of5 l0 1 L ,sa-

INVENTOR WlLLl HEYER, FRIEDRICH BRINKMANN Jan. 14, 1969 w. HEYER ET AL V 3,421,795

FLUID PRESSURE SUPPLY SYSTEM Filed May 31, 1967 Sheet 3 of 5 INVENTOR 'WILLI HEYER, FRIEDRICH 'BRINKMANN United States Patent US. 01. 299-32 22 Claims Int. Cl. E21c 29/02,- E2111 11/00 ABSTRACT OF THE DISCLOSURE Pressure fluid supply system for longwall mining operations including a pressure fluid flow conduit circuit for supplying fluid to a series of shifting means composed of coacting pistons and cylinders which are to be arranged in spaced apart disposition along a guide for a mining machine to urge the guide against the mine face to enable the mining machine to engage operatively such mine face to extract material therefrom, at least some of the shifting means having corresponding quantity-regulating metering means, e.g. a double acting piston pump, flow-connected therewith in the circuit either upstream or downstream of the shifting means therefor, to determine the fluid quantity flowing through the particular shifting means, and metering valve control means to control the flow of fluid through the metering means to operate the metering means and thereby to regulate the fluid quantity flowing through the associated shifting means, whereby to achieve substantially unyielding urging via such shifting means of such guide even during passage of the mining machine thereat and controlled advance of the guide and in turn of the mining machine in the direction of the mine face in dependence upon the quantity regulation by the metering means of the fluid flowing through the corresponding shifting means associated therewith.

The present invention relates to a pressure fluid supply system for a series of shifting devices which are arranged to press a guide means for a mineral winning machine against a longwall working face so that the winning machine moved along on the guide means engages the working face with its cutting tools under adequate pressure and sufliciently deeply.

In the winning or extraction of mineral, such as coal, especially in longwall mining operations, it is known to move winning or mining machines which work by cutting or skimming, for example mining planers, back and forth along the wining face or mine face and to guide these mining machines on conveying means, rails or other longitudinal guides. In this method of winning mineral, the mining machines must be pressed constantly against the mine face, so that the mining machine engages with the desired skimming or cutting depth into the mine face. For this purpose, use is made predominantly of hydraulic shifting devices, e. g. piston-cylinder means, which act upon an abutment extending along the mine face being worked, this abutment being formed in most cases by the conveyor which serves to convey away the won material (see, for instance, US. Patents 2,745,651 and 3,192,722).

It is known to permit the shifting devices to engage the conveyor at intervals. A common pressure conduit normally connects the individual shifting devices in such manner that the mining machine, especially if it is a coal plough or planer, forces back the conveying means or other guide in the region of the planer passage and thus pushes the piston rods into the cylinders of the shifting devices. After the passage of the planer, the piston rods "ice push out again and press the conveyor against the mine face as before, since the pressure fluid supply conduits of the shifting devices are connected in common with one another. This action, which is known as so-called breathing of the conveyor or other guide, occurs to a greater extent in the case of the use of mining machines which require a lane or planer alley between the mine face and guide (for example the conveying means), to permit the extraction or loading work to be performed, since this alley on the one hand is necessary during the passage of the mining machine yet on the other hand closes again immediately after the passage of the mining machine due to the pressure of the shifting devices against the guide.

It is in fact known to make the shifting devices of mechanical nature, for example by means of a ratchet device, and thus prevent the rearward deviation of the shifting devices (see German Patent 970,191), but the complicated and expensive operation of such shifting devices is no longer tolerable from a practical standpoint with modern mining methods.

However, as is known, the so-called breathing action of the guide has decisive disadvantages. Thus, for example, this action stresses the guide to a great extent. Furthermore, the mining machine with its associated guide can be controlled on the mine face only with very great difliculty. Where a conveying means is used as a guide and a planer provided with a sword or keel is used, the conveying means lifts considerably during the passage of the planer, and after the passage slides itself on to the fine coa l remaining in the planer alley. The mining machine and the traction means used to conduct such machine back and forth along the mine face are greatly stressed, with the result that damage occurs to the traction means such as a chain or to the traction drive (for example shear bolt fractures). Moreover, the shifting devices must be driven with a hydraulic pressure which is considerably below the hydraulic pressure of other hydraulic units necessary for the mining operation (such as hydraulic prop supports), so that the pressure of the shifting devices against the mine face does not become too great.

In recognition of these disadvantages it has been proposed, when using a plough or planer, to dispense with the sword or keel engaging beneath the conveying means and to guide the planer with a constant cutting allowance on a rail or other guide which in turn rests constantly against the mine face, as shown in German published specification 1,216,222. While the arrangement described in this German specification overcomes the above described disadvantages, it does involve dispensing with the use of a planer keel and thus in the usual case also at the same time dispensing with the goaf-side guidance of the traction drive means for the planer, which is known to be advantageous.

Finally, it is known in shifting devices for longwall conveyors, to use shifting cylinders which are chargeable through a manually operated piston pump or gear pump. In this case to each shifting device there is allocated a pump which While rendering possible the charging of the shifting device in small part-strokes is however uneconomical due to the necessary manual operation and expensive constructional form. The use of this known device absolutely necessitates dispensing with the usual hydraulic leads disposed in the longwall gallery, which are recognized as advantageous (see German patent 1,062,656). This disadvantage is clearly recognized in such prior art proposal.

It is an object of the present invention to overcome the above-described disadvantages and to ensure that the guidance of the unining machine is preserved, without the necessity of dispensing with the use, for example, of a goaf-side guidance of the mining machine, especially via a planer keel engaging beneath the conveyor.

It is another object of the present invention to provide a pressure fluid supply system for a series of shifting devices, such as shifting piston-cylinder means, adapted to be arranged to urge substantially unyieldingly a guide means for a mining machine, such as a planer, against a longwall mine face so that the mining machine will engage such mine face under adequate pressure and sufliciently deeply during passage along the guide means, whereby to achieve a more uniform extraction of mineral despite variations in the quality of the seam being worked, such as changes in the degree of hardness or softness of the seam.

It is still another object of the present invention to provide a system of the foregoing type utilizing quantityregulating means, such as metering pump means, to determine the fluid flow to and/ or through such shifting devices and in turn to control the axial displacement of such shifting devices and thereby achieve unyielding abutment of such guide means against the mine face, even during passage of the mining machine thereat, as well as predetermined rates of advance of the guide means in the direction of the mine face after the mining machine has passed.

It is a further object of the present invention to provide a system of the foregoing type which includes means for controlling the direction of flow of the pressure fluid in the system for versatile operation and to provide for such quantity-regulation of the fluid flow through such shifting devices either upstream or downstream thereof in the system, with appropriate safeguards in the form of non-return and over-pressure valves disposed in the system to prevent undesired fluid back-flow in the system as well as excess counterpressure, such as that generated at the mine face during passage of the mining machine and transmitted via the guide means to the shifting devices.

It is a still further object of the present invention to provide an inexpensive, durable, and uncomplicated arrangement, simple to produce and relatively free from functional breakdown during operation.

Other and further objects of the present invention will become apparent from the within specification and ac companying drawings, in which:

FIG. 1 shows schematically in section a specific type of quantity-regulating device usable in accordance with the present invention;

FIG. 2 shows schematically a circuit diagram of a fluid flow system usable in accordance with one particular embodiment of the invention including a quantity-regulating device connected in the pressure line upstream of the shifting piston-cylinder means to be regulated; and

FIG. 3 shows schematically a circuit diagram of a fluid flow system usable in accordance with another particular embodiment of the invention including a quantity-regulating device connected in the pressure line downstream of the shifting piston-cylinder means to be regulated.

It has been found, in accordance with the present invention, that an advantageous and versatile pressure fluid supply system for longwall mining operations may now be provided which comprises pressure fluid flow conduit circuit means, a series of shifting means including coacting shifting piston and cylinder means flow-connected with said circuit means, said shifting means being. adapted to be arranged in spaced apart disposition along a guide means for a mining machine to urge such guide means against a mine face thereat to enable such mining machine to engage operatively such mine face to extract mineral therefrom, at least some of said shifting means each having operatively flow-connected therewith in said circuit means a corresponding pressure fluid quantity-regulating metering means which determines the pressure fluid quantity operatively flowing through the particular shifting means associated therewith and which is operated by pressure fluid from said circuit means, and metering valve control means operatively flow-connected with each said metering means to control the flow of pressure fluid through said metering means to operate said metering means and to regulate in turn the pressure fluid quantity flowing through the associated shifting means, whereby to achieve substantially unyielding urging via such shifting means of such guide means even during passage of the mining machine thereat and controlled advance of such guide means and in turn of the mining machine in the direction of the mine face, in dependence upon the quantity regulation by the metering means of the fluid flowing through the corresponding shifting means associated therewith.

The present invention thus achieves the above-noted objects by providing a quantity-regulating metering means or device which determines the inflow or outflow quantity of the hydraulic fluid which is allocated preferably to each shifting device. Hence, the extraordinary advantage is attained that a constant cutting allowance is settable by means of the guide of the mining machine. According to the quality of the mine face the quantity of hydraulic fluid supplied to the shifting device or removed from it can be readily adjusted by means of the quantity-regulating device. The shifting devices actually form to a certain extent a non-yieldable abutment which, after every pass age of the mining machine. shifts forward by an amount corresponding to the mining machine or the mine face newly exposed, without the entire guide of the mining machine being pressed against the mine face after the passage of the mining machine.

If a conveying means, such as a conventional double chain scraper conveyor, is used as guide, this conveying means no longer lifts itself away from the floor during the passage of the mining machine and can no longer slide onto the cushion of fine coal, so that very favorable guidance of the mining machine along the mine face is ensured.

The quantity-regulating device is connected according to one particular feature of the instant invention into the pressure conduit of the shifting device and includes a cylinder having a double-acting piston slidably guided therein, the movement of the piston being limited at each end of the cylinder by means of stop members, one of which is adjustable. Such adjustable stop can be a spindle, for example, which according to a further feature of the invention is provided with a scale indicating the stroke volume of the quantity-regulating device. Thus it is possible to adjust the individual shifting steps of the shifting device most exactly. Also, the possibility is provided of an exact orientation of the guide means with respect to the mine face, with maximum exploitation of the guide means or conveying means and of the mining machine.

According to another particular feature of the instant invention, into the return conduit of the shifting device there is connected a cylinder with float piston guided therein, the stroke volume being adjustable preferably by displacement of a cylinder head. In this case thus the quantity of fluid fed to the shifting device is determined in dependance upon the quantity of fluid removable therefrom, which then flows through the quantity-regulating device.

The shifting device operates in essentially the same manner whether use is made of a cylinder having a double-acting piston slidably guided therein, on the pressure side of the shifting piston-cylinder means, i.e. upstream thereof, or of a cylinder having a float piston slidably guided therein, on the exhaust side of the shifting piston-cylinder means, i.e. downstream thereof. Both such devices serve to regulate the quantity of pressure fluid, e.g. hydraulic oil, flowing to or through the shifting device, whereby to extend such device and in turn urge the guide means and mining machine against the mine face in a controlled manner.

According to a further feature of the present invention, in the pressure conduit associated with each shifting device there is provided a non-return valve which prevents the return flow of the pressure medium. It is advantageous here to arrange an adjustable over-pressure valve between each shifting device and the non-return valve provided in the pressure conduit of each shifting device, so that despite the almost unyieldable guidance, the mining machine or guide means or pressure fluid system is not damaged for example in the extraction of a heterogeneous mine face, i.e. one which is permeated with rock inclusions. The overpressure valve therefore responds, according to a further feature of the invention, only in the case where the return forces or counterforces met at the mine face can no longer be taken up by the mining machine, such as a mining planer.

Furthermore, it is advantageous if the shifting devices are chargeable with individual or common quantity-regulation, so that the possibility is provided of being able to extract mineral such as coal from the mine face even only over certain sections thereof.

The impulse emission for the quantity-regulated charging of one or more shifting devices can take place manually or automatically, preferably hydraulically, pneumatically or electrically, from a central control position, if desired. Independently of this, naturally the volumes of individual quantity-regulating devices can be adjusted, so that the orientation of the arrangement at the mine face can take place to a certain extent automatically.

According to a further feature of the instant invention one or more quantity-regulating devices can be disconnected from the system. This disconnectability can be effected by means of a blockable connection of the shifting device to the pressure conduit, such as by way of appropriate valves, whereby the quantity-regulating device may be by-passed, or it can be so formed that between the quantity-regulating device and shifting device there is arranged a control block, e.g. in the form of a multi-position valve which permits the control positions extend, retract and shut-off to be effected. Thus the possibility is provided of either extending individual shifting devices towards the guide means by a greater range than permitted with the quantity-regulating device, or retracting them completely, or shutting them off completely for example from the advancing function.

Thus the invention provides a method in which several shifting device act upon one abutment, such as a mining conveyor, while due to the quantity-regulated charging of several shifting devices a non-yielda-ble guide is formed which adjustably determines the distance between the mine face to be won and the shifting device.

Particular advantages of this method and of the means for carrying out such method are seen in the removal of the initially described disadvantages and especially in the fact that now it is possible, utilizing the pressure of hydraulic or pneumatic devices necessary also for operating other equipment for the extraction of mineral, to charge the shifting devices and thus to form a non-yieldable guide for the mining machine.

Referring to the drawing, in which more detailed representation of the mine face and of the mining machine has been omitted, a quantity-regulating metering means in the form of device 2 (see FIG. I) is shown which includes a cylinder 4 and a piston 5 which can slide back and forth between the stops 6 and 7. The pressure fluid for operating the quantity regulating device 2 is supplied and withdrawn according to choice through the conduits 17 and 18 to provide a metering piston pump action. The stroke volume of the quantity-regulating device 2 is adjustable by means of a spindle 8 extending in axially slidable sealed disposition through the corresponding end of cylinder 4 and provided with a scale 9 at the exposed outer end portion thereof. Stop 7 is fixed to the spindle inner end.

The pressure fluid supply system circuit as shown in FIG. 2 provides for the flow of pressure fluid from the pressure conduit 3 through the metering valve control means in the form of a control block 19, having the alternate flow valve portions 19a and 19b, and the conduit 18 into the quantity-regulating device 2, (such as that of FIG. 1 but here shown more schematically in the interests of clarity). The piston 5 in this case expels the'fluid situated in quantity-regulating device 2 through the conduit 17 via control block 19 and the shifting control valve in the form of the control block 16 into the shifting device 1 which is in the form of a double-acting piston-cylinder means. The control block 16, having the valve positions 16a, 16b and 160, is of such formation that the shifting device 1 can be shut off completely at position 16b as shown, or be provided with direct flow via positions 16a or 16c to either side of the piston thereof alternately, depending on which of the three valve positions of control block 16 is selected. In the case of inadmissibly high return forces or counterforces generated at the mine face, the pressure fluid flows through an over-pressure valve 13, schematically shown, into the return conduit 10. A further disconnect or by-pass valve in the form of a control block 15, having an open position 15a and a closed position 15b as shown, renders possible the direct charging of the shifting device 1, by the arrangement of the non-return valve 12, the quantity-regulating device 2 thus being bypassed. The entire shifting arrangement, including the shifting device 1 and the quantity-regulating device 2, can be operated from a central control position via a remote control valve 14: shown schematically.

Valve 14 is linked operatively by any suitable means with control block 19, such as hydraulic servo means, to displace block 19 from the normal spring-urged position 19a to the alternate flow position 19b, upon axial displacement from the closed flow position 14a to the open position 14b. On reverse actuation, block 19 returns to position 19a. Blocks 15 and 16 operate in similar fashion by axial displacement. Such displacement may be individual for blocks 15, 16 and 19, e.g. by manual actuation, or automatic, e.g. by remote control operation as shown for block 19. Also, several blocks 16 and/or 15 and/or 19 may be ganged, i.e. connected for joint and/or simultaneous actuation, to achieve a common urging effect along a given portion of the guide means being urged against the mine face.

In the illustrated embodiment according to FIGURE 2 a double-chain scraper conveyor 20 of the conventional type is indicated as the guide. The shifting device 1 bears for example through a drag prop 21 against the roof 22, but it can equally be supported on support frames, i.e. self-propelling pit props or frames or the like, if desired, and of course other guides such as a planer track may be used rather than a conveyor.

According to FIGURE 3 the shifting device 1 is connected directly to the pressure conduit 3' through a nonreturn valve 12 with the quantity-regulating device 2' located on the exhaust (downstream) side of the shifting device 1' rather than on the pressure (upstream) side thereof as in FIG. 2. The quantity-regulating device 2' comprises a float piston 5' which slides freely in the cylinder 4' and the stroke of which is adjustable by axially adjustable cylinder heads 11, 11 shown schematically, whereby to provide -a metering piston pump action. The possible extension distance of the hollow piston rod 23 is determined by the quantity of fluid receivable by the adjustable quantity-regulating device 2 and flowing out from the annular cylinder space 24 of the shifting device 1'. Over-pressure valve 13 corresponds in function to valve 13 of FIG. 2 to relieve excess pressures in device 2'. The quantity-regulating device 2 delivers the fluid through the control block 25, having the alternate flow positions 25a and 25b and corresponding in form and operation to control block 19 of FIG. 2, to the return conduit 10'. The control 'block 26 associated with the shifting device 1' combines the functions of blocks 15 and 16 of FIG. 2, more or less. Block 26 is axially slidable, e.g. by manual or automatic actuation as discussed above (as is block among the three control positions, i.e. position 27 (for achieving extension with stroke limitation of shifting device 1 according to the cutting depth), position 28 (for achieving extension without stroke limitation or correction of the cutting depth or alignment of the guide) and position 29 (for achieving retraction without stroke limitation or drawing up of the shifting device).

Thus, by reason of the presence of the metering means, e.g. quantity-regulating device, whether upstream or downstream of the shifting Imeans, e.g. shifting piston-cylinder means, the quantity of fluid passing through the shifting means may be regulated by simple actuation of the metering valve control means, e.g. control block 19 or 25, to attain limited extension (i.e. stroke amplitude) of the shifting means from the shifting means starting retracted position while withstanding (except in dependence upon the adjustable actuation pressure level of the overpressure valve) counterpressures exerted against the shifting means which would normally cause at least temporary receding or retraction thereof (i.e. stroke amplitude regression).

Advantageously, in accordance with the present invention, each metering means is provided with adjustment means for adjusting the quantity of pressure fluid which flows through the particular shifting means associated therewith.

Specifically, each metering means includes metering piston-cylinder means in the form of a cylinder having a double-acting piston operatively slidably received therewithin, the corresponding valve control means therefor being flow-connected therewith to supply pressure fluid alternately as intake to each side of said piston upon corresponding alternate actuation of such valve control means such that the pressure fluid in the cylinder on the correspondingly opposite side from the intake side is forced as exhaust therefrom, the pressure fluid stroke quantity as intake and exhaust corresponding to the fluid quantity flowin g through the associated shifting means.

In accordance with one embodiment of the invention, the adjustment means for the metering means may include an axially adjustable stop at a corresponding end of said cylinder to limit the movement of said piston therewithin. A stationary stop may be disposed at the opposite end of the cylinder from that having the adjustable stop and the adjustable stop may be in the form of a spindle. Preferably, such spindle extends outwardly through the corresponding wall of said cylinder and the extended end thereof contains a scale indicating the stroke volume of the metering piston-cylinder means in dependence upon the axial position in said cylinder of said adjustable stop.

In particular, the metering piston-cylinder means may be disposed in the circuit means upstream of the corresponding shifting means to control the supply of pressure fluid to such shifting means, or downstream thereof to control the exhaust of pressure fluid from such shifting means and thereby the supply of pressure fluid to such shifting means.

The piston may be a floating piston within the cylinder and the adjustment means may include an axially displaceable head at a corresponding end of said cylinder to limit the movement of said piston therewithin.

The circuit means may be provided with a nonreturn valve operatively positioned on the pressure side of each such shifting means, as well as an adjustable over-pressure valve operatively positioned between said shifting means and said non-return valve. Preferably, the over-pressure valve is adjusted to respond only when the pressure fluid backforce corresponds to an overpressure in the shifting means caused by excessive counterforces met by the mining machine at the mine face which are suflicient to displace the mining machine and the guide means therefor away from the-mine face and in turn change the fluid disposition within said shifting means.

As desired, each corresponding shifting piston of the shifting piston and cylinder means may be provided with an over-pressure valve for over-pressure flow communication between the corresponding cylinder portions on the axial sides thereof.

While the valve control means for the metering means may be individually operated, they may also be remotely operated by remote control means operatively connected with said valve control means for controlling said valve control means from a remote control position.

The circuit means may include disconnect by-pass valve means flow-connectable with said shifting means to disconnect said metering means from said circuit means and to permit direct bypass operation of said shifting means independently of said metering means. In particular, the disconnect valve means may include a direct by-pass valve and a three-position shifting control valve for said shifting means positioned operatively in said circuit means, said shifting control valve normally being in flow-connection with said metering means and upon actuation of said by-pass valve said shifting control valve being placed in direct by-pass flow-connection with said by-pass valve, such that said shifting control valve in one alternate position supplies fluid to one side of the shifting piston means of the shifting means, in another alternate position supplies fluid to the other side of said shifting piston means, and in a further alternate position shuts off said shifting means from all fluid flow. Alternatively, the disconnect valve means may include a three-position shifting control valve positioned operatively in said circuit means, such that said shifting control valve in one alternate position supplies fluid to one side of the shifting piston means of the shifting means and exhausts fluid from the other side of said shifting piston means Without any fluid flow through said metering means, in another alternate position supplies fluid to such other side of said shifting piston means and exhausts fluid from such one side of said shifting piston means without any fluid flow through said metering means, and in a further alternate position supplies fluid to one of said sides of said shifting piston means while passing exhaust fluid from the corresponding other side to said metering means via said valve control means.

Thus, a plurality of adjacent shifting means may be controlled, in accordance with the present invention, in unison by corresponding metering means to act in a nonyieldable manner and which may be extended in adjustable increments.

Regarding one specific embodiment of the present invention, the metering means is in the form of a double acting piston pump and said circuit means is provided with a shifting control valve for said shifting means, a non-return valve, an adjustable over-pressure valve, and a by-pass valve, said circuit means flow-connecting in turn said valve control means with said pump, said pump with said non-return valve, said non-return valve with said shifting control valve, and said shifting control valve with said shifting means, with said over-pressure valve being positioned operatively between said non-return valve and said shifting control valve and with said by-pass valve being positioned operatively in direct flow-connection with said shifting control valve downstream of said non-return valve and upstream of said over-pressure valve to permit by-pass direct operation of said shifting means independently of said pump.

Regarding another specific embodiment of the present invention, the metering means is in the form of a double acting pump and said circuit means is provided with a three position shifting control valve for said shifting means, a non-return valve, and an adjustable over-pressure valve, said circuit means flow-connecting said non-return valve with said shifting control valve, and in turn flowconnecting said shifting control valve in one alternate position with one side of the shifting piston means of said shifting means while permitting exhaust of fluid from the other side of said shifting piston means without any fluid flow through said pump, in another alternate position with such other side of said shifting piston means while permitting exhaust of fluid from such one side of said shifting piston means without any fluid flow through said pump, and in a further position with one of such sides of said shifting piston means while permitting exhaust of fluid from the other of such sides of said shifting piston means to pass to said valve control means for passage through said pump, with said over-pressure valve being positioned operatively in said shifting piston means for over-pressure flow-communication between the corresponding cylinder portion on the axial sides thereof.

Naturally,where various constructional parts have been defined in terms of means in the instant specification and/ or claims, such means have been illustrated in the accompanying drawings as specific elements, but in accordance with the present invention, such means contemplate any and all elements usable to achieve the combination arrangement of the invention, as the artisan will appreciate, so long as the disposition of the parts in question is maintained and any and all such constructional elements are contemplated herein just as if prolix enumeration thereof were set forth in detail herein.

It will be appreciated that the instant specification and drawings are set forth by way of illustration and not limitation and that various modifications and changes may be made without departing from the spirit and scope of the present invention which is to be limited only by the scope of the appended claims.

What is claimed is:

1. Pressure fluid supply system for longwall mining operations which comprises pressure fluid flow conduit circuit means, a series of shifting means including coacting shifting piston and cylinder means flow-connected with said circuit means, said shifting means being adapted to be arranged in spaced apart disposition along a guide means for a mining machine to urge such guide means against a mine face thereat to enable such mining machine to engage operatively such mine face to extract mineral therefrom, at least some of said shifting means each having operatively flow-connected therewith in said circuit means a corresponding pressure fluid quantityregulating metering means which determines the pressure fluid quantity operatively flowing through the particular shifting means associated therewith and which is operated by pressure fluid from said circuit means, and metering valve control means operatively flow-connected with each said metering means to control the flow of pressure fluid through said metering means to operate said metering means and to regulate in turn the pressure fluid quantity flowing through the associated shifting means, whereby to achieve substantially unyielding urging via such shifting means of such guide means even during passage of the mining machine thereat and controlled advance of such guide means and in turn of the mining machine in the direction of the mine face in dependence upon the quantity regulation by the metering means of the fluid flowing through the corresponding shifting means associated therewith.

2. System according to claim 1 wherein each such shifting means is provided with a corresponding metering means and valve control means.

3. System according to claim 1 wherein said valve control means for said metering means are individually operated.

4. System according to claim 1 wherein said valve control means for said metering means are remotely operated by remote control means operatively connected with said valve control means for controlling said valve control means from a remote control position.

5. System according to claim 1 wherein a plurality of adjacent shifting means are controlled in unison by corresponding metering means to act in a non-yieldable manner and which may be extended in adjustable increments.

6. System according to claim 1 wherein said metering means is in the form of a double acting piston pump and said circuit means is provided with a shifting control valve for said shifting means, a non-return valve, an adjustable over-pressure valve, and a by-pass valve, said circuit means flow-connecting in turn said valve control means with said pump, said pump with said non-return valve, said non-return valve with said shifting control valve, and said shifting control valve with said shifting means, with said over-pressure valve being positioned operatively between said non-return valve and said shifting control valve and with said by-pass valve being positioned operatively in direct flow-connection with said shifting control valve downstream of said non-return valve and upstream of said over-pressure valve to permit by-pass direct operation of said shifting means independently of said pump.

7. System according to claim 1 wherein said metering means is in the form of a double acting piston pump and said circuit means is provided with a three position shifting control valve for said shifting means, a non-return valve, and an adjustable over-pressure valve, said circuit means flow-connecting said non-return valve with said shifting control valve, and in turn flow-connecting said shifting control valve in one alternate position with one side of the shifting piston of said shifting means while permitting exhaust of fluid from the other side of said shifting piston means without any fluid flow through said pump, in another alternate position with such other side of said shifting piston means while permitting exhaust of fluid from such one side of said shifting piston means without any fluid flow through said pump, and in a further position with one of such sides of said shifting piston means while permitting exhaust of fluid from the other of such sides of said shifting piston means to pass to said valve control means for passage through said pump, with said over-pressure valve being positioned operatively in said shifting piston means for over-pressure flow-communication between the corresponding cylinder portions on the axial sides thereof.

8. System according to claim 1 wherein said circuit means includes disconnect by-pass valve means flow-connected with said shifting means to disconnect said metering means from said circuit means and to permit direct bypass operation of said shifting means independently of said metering means.

9. System according to claim 8 wherein said disconnect valve means include a direct by-pass valve and a threeposition shifting control valve for said shifting means positioned operatively in said circuit means, said shifting control valve normally being in flow-connection with said metering means and upon actuation of said by-pass valve said shifting control valve being placed in direct by-pass flow-connection with said by-pass valve, such that said shifting control valve in one alternate position supplies fluid to one side of the shifting piston means of the shifting means, in another alternate position supplies fluid to the other side of said shifting piston means, and in a further alternate position shuts off said shifting means from all fluid flow.

10. System according to claim 8 wherein said disconnect valve means includes a three-position shifting control valve positioned operatively in said circuit means, such that said shifting control valve in one alternate position supplies fluid to one side of the shifting piston means of the shifting means and exhausts fluid from the other side of said shifting piston means without any fluid flow through said metering means, in another alternate position supplies fluid to such other side of said shifting piston means and exhausts fluid from such one side of said shifting piston means without any fluid flow through said metering means, and in a further alternate position supplies fluid to one of said sides of said shifting piston means while passing exhaust fluid from the corresponding other side to said metering means via said valve control means.

11. System according to claim 1 wherein each said metering means is provided with adjustment means for adjusting the quantity of pressure fluid which flows through the particular shifting means associated therewith.

12. System according to claim 11 wherein each said metering means includes metering piston-cylinder means in the form of a cylinder having a double-acting piston operatively slidably received therewithin, the corresponding valve control means therefor being flow-connected therewith to supply pressure fluid alternately as intake to each side of said piston upon corresponding alternate actuation of such valve control means, such that the pressure fluid in the cylinder on the correspondingly opposite side from the intake side is forced as exhaust therefrom, the pressure fluid stroke quantity as intake and exhaust corresponding to the fluid quantity flowing through the associated shifting means.

13. System according to claim 12 wherein said metering piston-cylinder means is disposed in the circuit means upstream of the corresponding shifting means to control the supply of pressure fluid to such shifting means.

14. System according to claim 12 wherein said metering piston-cylinder means is disposed in the circuit means downstream of the corresponding shifting means to control the exhaust of pressure fluid from such shifting means and thereby the supply of pressure fluid to such shifting means.

15. System according to claim 14 wherein said piston is a floating piston within said cylinder and said adjustment means includes an axially displaceable head at a corresponding end of said cylinder to limit the movement of said piston therewithin.

16. System according to claim 12 wherein said adjustment means include an axially adjustable stop at a corresponding end of said cylinder to limit the movement of said piston therewithin.

17. System according to claim 16 wherein a stationary stop is disposed at the opposite end of said cylinder from that having said adjustable stop, said adjustable stop being in the form of a spindle.

18. System according to claim 17 wherein said spindle extends outwardly through the corresponding wall of said cylinder and the extended end thereof contains a scale indicating the stroke volume of the metering piston cylinder means in dependence upon the axial position in said cylinder of said adjustable stop.

19. System according to claim 12 wherein said circuit means is provided with a non-return valve operatively positioned on the pressure side of each such shifting means.

20. System according to claim 19 wherein each corresponding shifting piston means of said shifting piston and cylinder means is provided with an over-pressure valve for over-pressure flow-communication between the corresponding cylinder portions on the axial sides thereof.

21. System according to claim 19 wherein said circuit means is provided with an adjustable over-pressure valve operatively positioned between said shifting means and said non-return valve.

22. System according to claim 21 wherein said overpressure valve is adjusted to respond only when the pressure fluid backforce corresponds to an overpressure in the shifting means caused by excessive counterforces met by the mining machine at the mine face which are sufficient to displace the mining machine and the guide means therefor away from the mine face and in turn change the fluid disposition within said shifting means.

References Cited UNITED STATES PATENTS 2,859,022 11/1958 Frye 6l45 3,120,105 2/1964 Kibble et al. 61-45 3,309,880 3/1967 Potts et al. 299-32 X 2,692,767 10/1954 Slomer 299--75 ERNEST R. PURSER, Primary Examiner.

U.S. Cl. X.R. 

